spectrum of the fibrous volcanic glass is close to those shown in Fig. 4.2c and
Fig. 4.3e.
4.2.5 Berry-Like Volcanic Glass
Mt. Fuji emits scoriaceous tephra (Kobayashi et al. 2007; Miyaji 2002). Soil
horizons of A1 to C were formed from Hoei, and horizons of 2A1 from Jogan tephra
(Fig. 4.5a). This soil is used as farmland to grow vegetables (Fig. 4.5b). Figure 4.5c
shows the 0.5–0.2 mm fraction of the scoriaceous Jogan tephra (2A1 horizon of
Fig. 4.5a). This particle-size fraction is colorful, displaying dark-colored scoria
(Fig. 4.6), red-colored scoria (Fig. 4.7), olivine (Fig. 2.4), and others.
Figure 4.6 shows an example of a scoria particle or colored volcanic glass. The
particle is dark and has many concavities (Fig. 4.6a, b). The EDX spectrum
(Fig. 4.6c) of the dashed area (Fig. 4.6b) shows that Mg, Al, Ca, and Fe concentrations are high, and that the Si concentration is low compared with non-colored
Fig. 4.4 Fibrous volcanic glass. (a) The Ito pyroclastic flow deposit (29 ka), (b) fibrous volcanic
glass particles separated from the air-dried Ito pyroclastic flow deposit, (c) the SEM image of an
edge of fibrous volcanic glass, and (d) close-up of the sampled pyroclastic flow deposit of the EDX
spectrum of the dashed square
64
4 Non-crystalline Inorganic Constituents of Soil